Colloidal molybdenum complexes prepared by ketone extraction



United States Patent Ofifice 3,140,997. Patented July 14, 1964 3,140,997 CQLLOEDAL MQLYBDENUIV! CUMPLEXES PREPARED BY KETQNE EXTRACTION John A. Price, Westfieid, N.J., assignor to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Dec. 7, 1961, Ser. No. 157,858 Claims. (61. 25233) The present invention concerns a novel process for preparing colloidal molybdenum complexes which involves dispersing a ketone extract of a molybdenum compound in an oil solution of a surface active or dispersant material. The complexes are particularly useful for addition to lubricating oil compositions to impart wear-reducing properties thereto.

For some time it has been known that various compounds of molybdenum, and particularly the sulfides, are desirable additives for lubricating oils because of their ability to reduce friction and hence to minimize wear of the parts being lubricated. Certain molybdenum complexes also have desirable properties of this nature. Molybdenum sulfide dispersions can be prepared by grinding the material to exceedingly fine particle size and then dispersing the particles in a lubricating oil medium. Such dispersions are not completelysatisfactory, however, because the particles of molybdenum sulfide tend to settle out either While the dispersion is in storage or while it is being used. For this reason there has been a need for more stable dispersions of molybdenum sulfide or, alternatively, a need for compositions that possess the wear- Ieducing properties of molybdenum sulfide and at the same time are free of the unstable nature of the molybdenum sulfide dispersions of the prior art.

While it has recently been found that colloidal dispersions of molybdenum sulfide can be prepared in situ in lubricating oils by reacting an aqueous solution of the molybdate with hydrogen sulfide in a lubricating oil medium containing a dispersant material and subsequently removing water, that process carried with it the limitation that in order to operate at high molybdenum levels more dispersant was necessary.

The most effective dispersants are derived from phosphorus-sulfide-treated hydrocarbons in conjunction with 4 compounds of barium. Each of these elements, i.e., phos phorus, sulfur and barium, may be objectionable in specific situations where their concentration levels may be relatively high. For example, in two-stroke-cycle engines such as outboard motors, phosphorus has a deleterious effect on spark plug life. High barium levels are objectionable in many instances because they tend to increase combustion chamber deposits. Sulfur in active form, as in the case of phosphosulfurized hydrocarbons, mayhave detrimental effects if present in high concentrations. Hence it is frequently desirable to minimize the concentration levels of certain dispersants or detergents.

In accordance with the present invention it has been found that colloidal complexes having relatively high concentrations of molybdenum in proportion to the dispersant can be prepared by extracting an aqueous acidifiedsolution of a molybdenum compound including molybdic acid and molybdate salts such as ammonium molybdate with a ketone and then dispersing the ketone extract in an oil-soluble dispersant. Before the ketone is removed, the dispersion is preferably treated with a quantity of hydrogen sulfide to form at least some molybdenum sulfide as a colloidal dispersion in the product. The complex that is formed probably contains other molybdenum compounds such as molybdenum blue and molybdenum oxides. The exact structure of the complex has not been determined, and it is not intended that the scope of the invention be limited merely to molybdenum sulfide dispersion.

Not only does the process of this invention lead to higher molybdenum concentration levels, but it also enables wider versatility in the selection ofdispersants that may be used; e.g., calcium compounds where barium compounds are objectionable; sulfonate detergents (nonlabile sulfur) or sulfur-free dispersants where active sulfur compounds (e.g., phosphosulfurized compounds) are objectionable. Alternatively, a high molybdenum concentration obtained in accordance with the present invention, even if the dispersant had certain drawbacks, would require a relatively small amount of the latter dispersant and would permit the concurrent use, in the finished lubricant, of a second, more desirable dispersant from the standpoint of deleterious effects in use, even though the the second dispersant might be less satisfactory for preparing the colloidal dispersion of molybdenum compounds in accordance with this invention, thus giving a highly satisfactory composition from every standpoint.

Among the molybdenum salts that may be used in this invention are included ammonium molybdate, sodium molybdate, potassium molybdate, barium or magnesium molybdate and molybdates of other metals such as zinc and cadmium. As has been stated, molybdic acid may be used also. It is likewise possible to employ molybdenum trioxide by dissolving it in aqueous ammonia followed by treatment with hydrochloric acid. In essence the M00 is first converted to ammonium molybdate.

The general procedure followed in practicing the invention is as follows. The molybdate may be dissolved in the minimum amount of water necessary for complete solution, although the amount of water may range from 4 to '10 parts by weight per part of molybdate. Then suflicient mineral acid such as aqueous HCl may be added to furnish a solution having a normality in the range of' mal, there is a tendency for excess chlorine to appear in the product when. HCl is used, while if it is below 4 normal, the molybdenum utilization, i.e., the proportion of molybdenum in the product to the molybdenum used in the process, tends to be poor. The solution is then extracted with a ketone. After a period of agitation for proper contact with the ketone and then a period of settling for separation, the ketone extract layer is added to a suitable dispersant. Contacting temperatures and mixing rates are controlled so as to prevent foaming problems.

The ketone extraction step and the dispersant contacting step may in general be conducted at temperatures in the range of from about 40 to about 100 F. although temperatures outside this range are not excluded. The preferred temperature range is from about 50 to about F.

Following the dispersant contacting step the ketone may be removed by heat and vacuum or by heat and inert gas blowing, nitrogen being a suitable inert gas. In the preferred process, however, prior to ketone removal, the mixture of ketone extract and dispersant is given an H 8 treatment by blowing it with a stream of hydrogen sulfide at a temperature in the range of about 50 to 80 F. for sutlicient time to convert at least some of the molybdenum to the sulfide. Thereafter the ketone and unreacted H 8, as well as any water that is present are removed by heating and by purging with an inert gas. For higher boiling ketones vacuum may be applied as a substitute for or as an added step to the inert gas purge. The final stripping temperature will depend somewhat on the ketone used a batch process, a continuous process may also be used wherein each of the steps will be conducted in a separate zone. The aqueous layer obtained during the separation step following the ketone extraction step may be recycled to the zone where molybdate is mixed with acid. Also the ketone that is removed during the stripping operation may be re-used in the process.

In the extraction step the ratio of ketone to aqueous solution will ordinarily be within the range of 1 volume of ketone and 2 volumes of aqueous mixture to 2 volumes of ketone and 1 volume of aqueous mixture, although ratios outside this range are not excluded. Ketone extraction may be conducted in a single stage or in multiple stages. Countercurrent extraction may also be used.

The ketones that are employed in practicing the present invention must be water-insoluble, they must be capable of extracting the molybdenum from the acidified aqueous solution, they must be compatible with the oil-soluble dispersant, and they must not deposit molybdenum sulfide from solution when the mixture of extract and diseprsant is treated with H 5. Ketones of at least 4 carbon atoms satisfy these requirements, and ketones having as many as 10 carbon atoms may be used. Those ketones that are particularly useful include methyl isobutyl ketone, methyl isoamyl ketone, and methyl hexyl ketone. The use of mixed ketones is also contemplated.

The dispersant used in the practice of this invention should have sufiicient alkalinity and should be used in a sufiicient quantity to neutralize the free acid in the ketone extract. Also, the dispersant should be oil soluble. The ratio of dispersant to molybdenum will depend largely on the basicity of the dispersant. Dispersants that can be used include metal sulfonates, metal carbonate sols and reaction products of metal oxides and/ or hydroxides with phosphosulfurized hydrocarbons.

The sulfonates used as dispersants in practicing this invention are the oil-soluble alkaline earth metal salts of high molecular weight sulfonic acids obtained by the sulfonation of either natural or synthetic hydrocarbons. Sulfonic acids can be prepared by treating lubricating base stocks with concentrated or fuming sulfuric acid in a conventional manner to produce oil-soluble mahogany acids. These sulfonic acids generally have molecular weights in the range of about 300 to 700. Petroleum sulfonates are well known in the art. Suitable sulfonic acids can also be produced by sulfonating alkylated aromatic hydrocarbons such as benzene, toluene, and xylene alkylated with olefins or olefin polymers. For example, sulfonated didodecyl benzene may be used.

Specific examples of sulfonates suitable for practicing this invention include calcium petroleum sulfonate, barium petroleum sulfonate, calcium di-C alkyl benzene sulfonate, barium di-C alkyl benzene sulfonate and calcium C alkyl benzene sulfonate. The C alkyl groups can be derived from diisobutylene, the C alkyl groups can be obtained from tripropylene and the C alkyl group can be obtained from tetraisobutylene. It is preferred to use the so-called high alkalinity type of sulfonate, which is prepared by reacting metal base in excess of that required for simple neutralization of the sulfonic acid to form an alkaline product which can then be treated with carbon dioxide to reduce its free alkalinity and form a substantially neutral final product. It is believed that the high alkalinity sulfonates are primarily dispersions of metal carbonates in the neutral sulfonates.

The reaction products of phosphosulfurized hydrocarbons with alkaline earth metal oxides or hydroxides can be prepared by first treating a hydrocarbon with the phosphorus sulfide and then reacting the product with an alkaline earth hydroxide or oxide, for example barium hydroxide, preferably in the presence of an alkyl phenol or an alkyl phenol sulfide and also preferably in the presence of carbon dioxide.

The phosphosulfurized hydrocarbons may be prepared by a reaction of a sulfide of phosphorus such as P with a suitable hydrocarbon material such as a terpene, a heavy petroleum fraction or a polyolefin, the latter having a Staudinger molecular weight in the range of 500 to about 200,000 and containing from 2 to 6 carbon atoms per olefin monomer. Particularly preferred are the polybutenes having Staudinger molecular weights in the range of about 700 to about 100,000. Preferably the phosphosulfurized hydrocarbon is prepared by reacting approximately 4 moles of the hydrocarbon base stock with 1 mole of phosphorus pentasulfide under anhydrous conditions at temperatures from about 150 to about 600 F. for from about /2 to 15 hours. The preparation of phosphosulfurized hydrocarbons is more fully described in US. Patent 2,875,188.

While the dispersion of the ketone extract of the acidic molybdate in the oil-soluble dispersant or detergent can be carried out in the presence of the latter material per se, it is more convenient to conduct the dispersion in an oil concentrate of the detergent or dispersant. Such concentrates usually contain from about 10 to about wt. percent, preferably 2060 wt. percent, of the surfactant in a lubricating oil. The lubricating oil may be either a mineral oil or a synthetic oil, the latter including diesters, complex esters, polysilicones, polyglycols and the like.

The nature of this invention, the manner in which it may be practiced, and the advantages accruing from the use of the ketone solvents will be understood and appreciated from the following examples.

EXAMPLE 1 The extraction efiiciency of various ketones for removing molybdenum from acidified aqueous solutions was determined in the following manner. In each instance, 1 gram of ammonium molybdate was dissolved in 6 cc. of 6 normal HCl. The acidified solution was then extracted in a separatory funnel with 10 cc. of ketone for 1 minute. The organic layer was then separated and was evaporated to dryness on a steam bath with the aid of a stream of nitrogen and the resulting residue was weighed to determine the quantity of material that had been ex tracted. The results obtained are given in Table I.

Table l EXTRACTION EFFICIENCY OF VARIOUS KETONES EXAMPLE 2 Molybdenum complexes may be prepared in accordance with the present invention by use of the following procedure: 1 part by weight of ammonium molybdate is mixed with 6 parts of 6 normal hydrochloric acid. This solution is cooled to about 80 F. and extracted with 10 parts of ketone. Separation into two layers is permitted and the extract layer is removed and stirred into 5 parts by weight of a dispersant. The dispersion may then be heated and stripped with gases to remove ketones and water. Preferably the dispersion is first treated with the proportion of at least one atom of sulfur per atom of molybdenum. The amount of H S used will depend on the amount of sulfur desired in the product, which may vary from less than 1 wt. percent to 4.5% or more in the additive concentrate. After the hydrogen sulfide treatment, an inert gas such as nitrogen is used to remove excess H 8 and the product is then filtered.

EXAMPLE 3 A phosphosulfurized hydrocarbon was prepared by reacting 100 parts by weight of a polybutene having an average Staudinger molecular weight of about 940 with parts by weight of phosphorus pentasulfide for about 8 hours at 4254 50 F the mixture being stirred and blown with nitrogen during the reaction. The resulting phosphosulfurized polybutene analyzed about 3.5 wt. percent phosphorus and about 6.6 wt. percent sulfur. Its viscosity at about 210 F. was about 20,000 SSU.

A dispersant concentrate was then prepared in the following manner. A blend was prepared consisting of 19.8 parts by weight of the phosphosulfurized polybutene, 6.5 parts by weight of nonyl phenol, 1.6 parts by weight of ammonium sulfonate of about 450 mol. wt. and 41.7 parts by weight of a neutral mineral oil of 150 SSU viscosity at 100 F. To this was added at a temperature in the range of 100-130 F., 4.4 parts, by weight of commercial ammonium hydroxide of 29% NH content. Then 1 part by weight of water and 16 partsrby. weight of calcium hydroxide were added at a temperature of 120150 F., followed by the addition of 9 parts by weight of CO over a period of 3-4 hours at a temperature in the range or" 145-160 F. The mixture was thereafter dehydrated by heating to a final temperature of about 370 F. and then filtered. The filtered product had the following weight percent composition:

Ca 9.0 CO 12.0 Phosphosulfurized hydrocarbon 22.5 Nonyl phenol 7.4 Neutral mineral oil 47.4 Ammonium sulfonate 1.7

EXAMPLE 4 The efiiciency of various ketones for preparing molybdenum complexes in accordance with the present invention was determined as follows. An aqueous solution was prepared in each instance consisting of grams of ammonium molybdate, 75 cc. of water, and 75 cc. of 12 normal hydrochloric acid. This solution was then extracted at 50 F. with 250 cc. of the particular ketone being tested. The solvent layer was then separated and dispersed in 125 grams of the dispersant concentrate of Example 3. The mixture was treated with 50 grams of hydrogen sulfide added over a period of minutes. After ketone removal the product was filtered. The particular ketones used and the molybdenum, sulfur and chlorine analyses obtained on the products are given in Table II. The final entry in the table is from a run in which the H 8 treating step was omitted. Where mixed ketones are shown in the table the ratios given are on a volume basis.

Table II Extraction Solvent Percent Percent Percent Mo S C Diisobutyl Ketone 2. 36 1. 69 1. 15 Methyl Isobutyl Ketone 6. 91 1. 77 5. 3 50/50 MIBK/DIBK 2. 75 2. 38 3. 32 Ethyl Amyl Ketone 2. 42 2. 49 1. 54 Methyl Amyl Ketone 6. 49 3. 79 4. 90 Butyl Ethyl Ketone 4. 15 3.19 3. 48 75/25 MHK MIBK 4. 80 3. 39 3. 91 Methyl Hexyl Ketone 5. 89 3. 69 3. 52 Methyl Isoamyl Ket0ne 6. 4.1 3.59 5. 90 50/50 MIBK MHK 6.19 3. 99 4. 77 Methyl Isobutyl Ketone (No H S) 5. 45 1. 10 4.12

EXAMPLE 5 The procedure of Example 4 was followed except that 8 N hydrochloric acid was used. The ketone employed was methyl isobutyl ketone. The additive concentrate product analyzed 8.86 wt. percent Mo, 2.07 wt. percent S, and 4.47 wt. percent Cl.

EXAMPLE 6 A crankcase lubricant is prepared by adding to a high viscosity index SAE 1OW30 motor oil, containing a copolymeric type viscosity index improver and conventional detergent-inhibitors and antioxidants, sufiicient of the concentrate of Example 5 to supply 0.025 weight percent of molybdenum.

Concentrates containing from about 2 to about 9 weight percent of molybdenum and from about 20 to about 60 weight percent of dispersant (on an active ingredient basis) in oil are readily prepared by the techniques of this invention. These concentrates can then be added to lubricating oil compositions to supply in the finished lubricants from about 0.01 to about 1 weight percent of molybdenum. In grease formulations suificient of the additive may be used. to furnish as much as 2 weight percent of molybdenum. In crankcase lubricants the additive will usually be employed in such concentrations that from about 0.01 to about 0.1 weight percent of molybdenum will be present.

Although the antiwear additives of this invention are primarily intended for use in lubricating oils designed for automotive crankcases, they may also be employed in other hydrocarbon oil compositions including turbine oils, various industrial oils, hydraulic fluids, transmission fluids and the like.

The oil compositions may contain other additives such as detergents, sludge dispersers, viscosity index improvers, e.g., polymethacrylates, polybutenes, etc., antioxidants such as phenyl-alpha-naphthylamine, alkyl phenols, bis phenols and the like, pour point depressants, dyes, and other additives for improving the properties of the compositions.

The additives of this invention are particularly applicable for use in lubricating oil compositions containing viscosity index improvers and detergent-inhibitors. The function of the latter is to prevent or minimize sludge formation as well as to hold in suspension sludge that may be formed in crankcase oils under conditions of low speed, low temperature operation, as in stop-and-go driving. In performing their function as sludge inhibitors and sludge dispersers, the detergent-inhibitors keep the wearing surfaces particularly clean and for this reason contribute to a higher degree of wear than would occur if no detergentinhibitor were present. This problem of wear with high detergency oils shows up particularly in the valve train of automotive engines, and especially in the valve lifter mechanism, where pressures as high as 50,000 to 100,000 p.s.i. can exist between the valve lifter and its actuating cam. The additives of the present invention are particularly effective for reducing wear in this region of the engine when it is lubricated with a high detergency motor oil.

The lubricating oils to which the antiwear agents of the present invention may be added include not only mineral lubricating oils but various synthetic oils. The mineral lubricating oils may be of any preferred type including those derived from the ordinary paraffinic, naphthenic, asphaltic or mixed base mineral crude oils by suitable refining methods. Synthetic hydrocarbon lubricating oils may also be employed. Other synthetic oils include dibasic acid esters such as di-Z-ethyl hexyl sebacate, carbonate esters, glycol esters such as C oxo acid diesters of tetraethylene glycol, and complex esters as for example the complex ester formed by the reaction of 1 mole of sebacic acid with 2 moles of tetraethylene glycol and 2 moles of 2-ethyl hexanoic acid.

It is to be understood that the examples presented herein are intended to be merely illustrative of the invention and not as limiting it in any manner; nor is the invention to be limited by any theory regarding its operability. The scope of the invention is to be determined by the appended claims.

What is claimed is:

l. A process for preparing a stable colloidal complex containing molybdenum which comprises extracting an acidic aqueous solution of a molybdenum compound, selected from the group consisting of molybdic acid, ammonium salts of molybdic acid and metal salts of molybdic acid, with a ketone having in the range of 4 to 10 carbon 7 atoms, said acidic solution having been acidified with a mineral acid to an acidity within the range of 2 N to 12 N, dispersing the resultant ketone extract in an oil-soluble basic metal-containing dispersant having sufiicient alkalinity to neutralize the free acidity of said extract, and then removing the ketone from the dispersion.

2. Process as defined by claim 1 including the step of blowing H 5 through the dispersion.

3. Process as defined by claim 1 wherein said aqueous solution is acidified with HCl and has an acidity in the range from 4 N to 8 N.

4. Process as defined by claim 1 wherein said dispersant is employed as an oil solution.

5. Process as defined by claim 1 wherein said ketone stripping is effected by heating and blowing with an inert gas.

6. Process as defined by claim 1 wherein said dispersant comprises a high alkalinity metal salt of a hydrocarbon sulfonic acid having a molecular weight in the range of 300 to 700.

7. Process as defined by claim 1 wherein said dispersant comprises the reaction product of a phosphosulfurized hydrocarbon with a basic substance selected from the group consisting of alkaline earth metal oxides and alkaline earth metal hydroxides.

8. An additive concentrate for lubricating oil compositions comprising a mineral oil, from about 20 to about weight percent of an oil-soluble metal-containing dispersant, and from about 2 to about 9 weight percent of molybdenum in the form of a complex prepared by the process of claim 1.

9. Additive concentrate as defined by claim 8 wherein said extract has been treated with H 8 prior to removal of the ketone.

10. A lubricating oil composition comprising a major amount of a lubricating oil and sufficient of the concentrate of claim 8 to supply therein from about 0.01 to about 1 weight percent of molybdenum.

References Cited in the file of this patent UNITED STATES PATENTS 2,753,306 Fields July 3, 1956 2,758,089 Hoff et al. Aug. 7, 1956 2,987,478 Matson June 6, 1961 

1. A PROCESS FOR PREPARING A STABLE COLLOIDAL COMPLEX CONTAINING MOLYBDENUM WHICH COMPRISES EXTRACTING AN ACIDIC AQUEOUS SOLUTION OF A MOLYBDENUM COMPOUND, SELECTED FROM THE GROUP CONSISTING OF MOLYBDIC ACID, AMMONIUM SALTS OF MOLYBDIC ACID AND METAL SALTS OF MOLYBDIC ACID, WITH A KETONE HAVING IN THE RANGE OF 4 TO 10 CARBON ATOMS, SAID ACIDIC SOLUTION HAVING BEEN ACIDIFIED WITH A MINERAL ACID TO AN ACIDITY WITHIN THE RANGE OF 2 N TO 12 N, DISPERSING THE RESULTANT KETONE EXTRACT IN AN OIL-SOLUBLE BASIC METAL-CONTAINING DISPERSANT HAVING SUFFICIENT ALKALINITY TO NEUTRALIZE THE FREE ACIDITY OF SAID EXTRACT, AND THEN REMOVING THE KETONE FROM THE DISPERSION. 